feat: post-signup onboarding wizard (dietary/allergen prefs, notifications, skippable) (v0.77.0)

New accounts land on a 3-step wizard after signup — welcome, dietary preferences & allergens, notification opt-in — skippable at every step, shown once via a users.onboardingCompletedAt gate in the (app) layout. Existing accounts are backfilled as already-onboarded.

Also gives the allergen-preferences step a real write path: user_allergens previously only had a GDPR-export read.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/app/onboarding/page.tsx

@@ -0,0 +1,22 @@
+import { redirect } from "next/navigation";
+import { headers } from "next/headers";
+import { auth } from "@/lib/auth/server";
+import { db, users, eq } from "@epicure/db";
+import { OnboardingWizard } from "@/components/onboarding/onboarding-wizard";
+
+export default async function OnboardingPage() {
+  const session = await auth.api.getSession({ headers: await headers() });
+  if (!session) redirect("/login");
+
+  const dbUser = await db.query.users.findFirst({
+    where: eq(users.id, session.user.id),
+    columns: { onboardingCompletedAt: true },
+  });
+  if (dbUser?.onboardingCompletedAt) redirect("/recipes");
+
+  return (
+    <div className="container mx-auto px-4 py-8">
+      <OnboardingWizard />
+    </div>
+  );
+}